By way of example only, the following description relates to the insertion of probes into the ground.
Probes used to measure soil conditions take many forms and use different techniques for measuring soil properties. Capacitor based techniques are well known and involve the positioning of a capacitor type sensor (typically a pair of conductive rings) at a predetermined depth in the soil to make the measurements using the surrounding soil as a dielectric medium. A soil probe will typically have three to six such pairs located at various depths within a probe housing so as to collect data that, once analysed, will provide a soil profile of moisture and/or salinity as well as other soil properties either immediately or at intervals of time.
In particular the depth and extent of moisture penetration into the soil is of interest as is also the uptake of moisture from the soil by crops over time.
Thus the probe must be located in the soil to at least the required depth of the lowest sensor element, which typically requires a probe length of about 600 to 700 mm to be fully inserted into the soil.
Most importantly, the probe when placed in the soil, should be completely surrounded only by undisturbed soil. The presence of air gaps adjacent to the outer wall of the probe will disadvantage the measurement process since the air and water that collects in those gaps may bias the readings or in the worst case make the readings unusable.
Air gaps can occur as a result of poor installation technique and poor equipment. More particularly, the forces required to insert the probe to an appropriate depth can accidentally displace the end of the probe to the sides of the opening and this can make the opening non-circular and leave gouges in the side of the opening that become gaps after full insertion of the probe or a probe body. The soil is thus discontinuous with the outer surface of the probe, and a gap or gaps will exist into which air and/or soil water can collect. In use a measurement probe is located in a probe body.
One way in which to attempt to overcome the problems associated with insertion resistance and lack of a tight fit is to make the opening in the soil deeper so that resistance at the end of the insertion process is not as great, or alternatively or in addition make the fit of the tube to the opening in the soil as dose as possible. However, even these measures are not always successful or sufficient, as (depending on soil type) more soil than anticipated can be dislodged from the sides of the opening as the probe is inserted, the soil immediately surrounding the probe body is unnecessarily compacted and eventually when the probe is inserted to its lowest point, it still sometimes does not attain the required depth.
Dislodged soil in the above circumstance drops to the bottom of the prepared opening and builds up to a level that can, even with compression from above, resist the insertion of the probe to the required depth.
The provision of a pointed end on the inserted probe does not always suffice to ensure the most appropriate insertion force or success in obtaining the required depth.
The above mentioned problems are not always experienced, but if probes need to be removed each season so that the soil can be tilled, in all likelihood, problems of the above nature will occur. This is particularly the case for probes used in the soils of vegetable crops which need to be moved often since those crops are best grown in well tilled and cultivated ground, and have relatively short growing cycles.
The invention to be described herein will minimise or eliminate the problems described above and will also be useful in the placement of probes that use other than capacitor based techniques. It may also be useful in the placement of posts and other elongate structures into the ground.